Inhibition of MEK sensitizes human melanoma cells to endoplasmic reticulum stress-induced apoptosis
Inhibition of MEK sensitizes human melanoma cells to endoplasmic reticulum stress-induced apoptosis
复制标题
DOI：
10.1158/0008-5472.can-07-2047
复制
发表时间：
2007-10-15
期刊：
影响因子：
11.2
通讯作者：
Hersey, Peter
中科院分区：
文献类型：
--
作者：
Jiang, Chen Chen;Chen, Li Hua;Hersey, Peter
过去的研究表明，丝裂原活化蛋白激酶/细胞外信号调节激酶（ERK）激酶（MEK）/ERK的激活是黑色素瘤细胞对死亡受体介导的或凋亡介导的凋亡抵抗的常见原因。我们在这项研究中报告，MEK/ERK通路的抑制也敏感的黑色素瘤细胞内质网（ER）应激诱导的凋亡，这是介导的，至少部分，由caspase-4激活，并与抑制ER伴侣葡萄糖调节蛋白78（GRP 78）的表达。用ER应激诱导剂衣霉素或毒胡萝卜素治疗在大多数黑素瘤细胞系中没有诱导显著的细胞凋亡，但对这些药物的抗性被MEK抑制剂U 0126或MEK 1小干扰RNA（siRNA）逆转。当MEK被抑制时，ER应激诱导的细胞凋亡是caspase依赖的，caspase-4、caspase-9和caspase-3参与其中。Caspase-4似乎是顶端caspase，因为caspase-4活化发生在caspase-9和caspase-3活化之前，并且通过特异性抑制剂或siRNA抑制caspase-4阻断caspase-9和caspase-3的活化，而抑制caspase-9或caspase-3不抑制caspase-4活化。此外，Bcl-2过表达抑制caspase-9和caspase-3的活化，但对caspase-4的活化影响甚微。在用衣霉素或毒胡萝卜素处理之前和之后，MEK/ERK的抑制也导致GRP 78的下调，GRP 78与半胱天冬酶-4物理相关。此外，GRP 78的siRNA敲低增加了ER应激诱导的caspase-4活化和凋亡。两者合计，这些结果似乎有重要的意义，新的治疗策略，在黑色素瘤的组合剂，诱导ER压力和抑制剂的MEK/ERK途径。
Past studies have shown that activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK is a common cause for resistance of melanoma cells to death receptor-mediated or mitochondriamediated apoptosis. We report in this study that inhibition of the MEK/ERK pathway also sensitizes melanoma cells to endoplasmic reticulum (ER) stress-induced apoptosis, and this is mediated, at least in part, by caspase-4 activation and is associated with inhibition of the ER chaperon glucoseregulated protein 78 (GRP78) expression. Treatment with the ER stress inducer tunicamycin or thapsigargin did not induce significant apoptosis in the majority of melanoma cell lines, but resistance to these agents was reversed by the MEK inhibitor U0126 or MEK1 small interfering RNA (siRNA). Induction of apoptosis by ER stress when MEK was inhibited was caspase dependent with caspase-4, caspase-9, and caspase-3 being involved. Caspase-4 seemed to be the apical caspase in that caspase-4 activation occurred before activation of caspase-9 and caspase-3 and that inhibition of caspase-4 by a specific inhibitor or siRNA blocked activation of caspase-9 and caspase-3, whereas inhibition of caspase-9 or caspase-3 did not inhibit caspase-4 activation. Moreover, overexpression of Bcl-2 inhibited activation of caspase-9 and caspase-3 but had minimal effect on caspase-4 activation. Inhibition of MEK/ERK also resulted in down-regulation of GRP78, which was physically associated with caspase-4, before and after treatment with tunicamycin or thapsigargin. In addition, siRNA knockdown of GRP78 increased ER stressinduced caspase-4 activation and apoptosis. Taken together, these results seem to have important implications for new treatment strategies in melanoma by combinations of agents that induce ER stress and inhibitors of the MEK/ERK pathway.